The present invention relates to a construction of trunking. Trunking is used extensively to house electrical cable, fibre optic cables, air lines and general flexible carriers of fluids, electrical and other signals, hereinafter referred to generally as cables. It may be large or it may be relatively small in the form of circular cable ducting.
1. Field of the Invention
A problem with trunking is that very often conduits, which can be circular, are used to take off cabling from larger trunking or simply to bring cabling around factories. These conduits are often circular pipes which may be connected to channel shaped conduits, or indeed to other larger pipes. There are various problems then when fluid lines such as air lines or electric cable is taken off from the conduit, for example, to feed switchgear, motors and the like, or indeed in the transfer from one conduit to another.
A further problem is that the end face of the conduit is usually exposed such as to allow the ingress of dirt, moisture, and the like and this is, generally speaking, unhygienic. These also often have sharp edges leading to cable damage. Also, it is important to prevent the entry of rodents and insects.
2. Description of Prior Art
It is known, for example, to provide an electrical duct connector which has a pipe form of essentially the same cross sectional geometry as duct ends to be connected thereby. The duct connector has an outer wall diameter corresponding to the inner diameter of the duct ends so that the connector fits snugly into the duct ends. Such a connector is shown in U.S. Pat. No. 4,374,596 (Schlemmer et al). However, this is a relatively complex construction and involves a two part construction of pipe connector which is relatively inefficient. There are also proposed various devices for sealing the ends of electrical conduits such as that shown in U.S. Pat. No. 4,496,792 (Balkwell et al). Thus, the problems are already well known in the prior art and various solutions have been proposed. However, what is required is a simple and effective way of providing such trunking.
There is a need for a more hygienic way of leading electrical cable, fluid feed lines hereinafter referred to generally as transmission cables and the like, from such conduits to the positions in which they are required for the operation of the particular installation.
Further, and very importantly, there is a need to join such conduits together in such a manner as to provide a smooth transition between conduits without damage to other service carrying units that may be mounted therein. This is particularly important with electric power cables.
The present invention is directed towards overcoming the problems inherent in the present construction of trunking and in particular with the aforementioned trunking in the form of enclosed usually circular conduits. The term xe2x80x9cconduitxe2x80x9d is used in this specification to include all forms of conduit such as circular or rectangular pipes, sectioned pipes and fabricated trunking. While the description relates entirely to circular pipes, it will be easily appreciated how other types of conduit could use the present invention.
The invention provides a steel trunking assembly for housing transmission cables whether they be electric cables, air lines, fibre optic cables or indeed any cables that are flexible carriers of fluids, electrical and other signals. It is for lengths of steel conduit circular in cross-section having exposed end faces which are connected together by bored connectors. Each connector comprises at least two connector inlets, each for reception of the free end of a conduit. They can, for example, be T-pieces or multiple connectors. Each connector inlet has a conduit receiving bore extending from an open conduit receiving mouth to an internal conduit restraining stop. The conduit fits as a snug fit but not necessarily a tight fit within the bore. The invention provides a bored sleeve of plastics material which forms a force-fit within the conduit and the sleeve has a stop engaging annular flange projecting across the exposed end face of the conduit to engage against the internal conduit restraining stop. The sleeve effectively forms, firstly, the actual force-fit connector between the conduit and the connector and secondly, a smooth transition between connector and conduit for any transmission cables. The flange can extend laterally beyond the exterior of the conduit to form the force-fit and is ideally formed of a resilient plastics material.
A particularly suitable conduit restraining stop is formed by a gradual reduction in diameter of the conduit receiving bore where it connects with the remainder of the bore of the connector. With this latter embodiment, the sleeve has an outer stop facing surface to mirror the shape of the bore of the connector where its diameter is reduced to form the conduit restraining stop and in this way, the sleeve can form again a force-fit over the whole length of the stop.
The sleeve may have an enlarged tapering bore adjacent the flange to provide a smooth transition between the exterior of the flange and the conduit. Additionally, the tapering may occur adjacent each end of the bore.
In one embodiment of the invention, the steel trunking assembly has a transmission cable outlet device for the trunking comprising a hollow body member, an endplate incorporating a plurality of exit holes and a cable embracing connector in each exit hole. By having a tight cable embracing connector on each exit hole, it is possible to prevent the ingress of moisture and foreign bodies such as dust or rodents and insects. Such a transmission cable and outlet device will contain at least one of the conduit connectors already described as integral therewith for securing to a length of conduit.
A further embodiment of the invention provides a steel trunking cable where, instead of having the conduit engaging within the connector, the connector engages within the conduit. In this case, the sleeve will be mounted on the connector which will comprise at least two cylindrical connector spigots, each for engagement in the end of a conduit. Then, each connector spigot will have, on its outer surface, a conduit restraining stop. Further, such a steel trunking assembly may also include a transmission cable outlet device according to the invention.